Explosive charge assemblies



June 15, 1965 w. E. BROWN 3,

'EXPLOSIVE CHARGE ASSEMBLIES Filed March 31. 1961 3,l8,% Patented June 15, 1965 3,188,955 EXPLOSIVE CHARGE ASSElt HELEES Wiiiiam E. Brown, Richardson, Ten, assignor to The Western ornpany oi North America, Fort Worth, Tex,

a corporation of Delaware Filed Mar. 31, 1% Ser. No. 99,819 The portion of the term of the patent subsequent to Dec. 22, 1981, has been disciainied 22 Claims. (Ci. 1-32-24) This invention relates to an explosive charge assembly. More particularly, the invention relates to an explosive charge assembly for both military purposes and for perforating oil well casings and well boreholes.

The principle of the hollow charge or shaped explosive charge has been known for many years. The disclosure or this principle has been known since at least about 1792 and publications such as the May 1888 issue of Scribners Magazine have discussed the principle. The principle became known as the Monroe eifect in Eng land and the United States and as the Neurnann effect in Germany. In general, this principle or efi'ect takes advan tage of concentrating the forces from an explosive charge into a smaller area by providing a concave hollowing or shaping of the face of the explosive-directed towar the area to be penetrated.

Early in World War II a number of military weapons appeared based on a modification of the hollow charge principle. This modification resulted from the discovery that by lining the face of the charge having the hollowed area or cavity with a thin metal liner it became possible to perforate armor plate, concrete walls, or other structures, with a surprisingly small weight of explosive charge. Very often these new weapons took the form of a projectile with the lined hollow charge in the nose of the projectile. The hollow charge principle was employed in a number of light, low velocity, antitank weapons, including the well-known rocket-propelled Bazooka. Such projectiles had the advantage over the previous military projectiles in that their ability to perforate was practically independent of their striking velocity. Even hand placed or statically detonated hollow explosive charges were at least as effective in perforating armor plate as previous projectiles which detonate upon impact.

The scientific principles involved in these military devices of World War ii are discussed by Birkhotf et al. in Journal of Applied Physics, vol. 19, pages 563582 (June 1948). The application of the hollow charge principle was not limited to military explosives but was logically extended to oil well perforating charges. An example of such a construction is that disclosed by Davis et al. US. Patent No. 2,399,211; Muskat et al. US. Pat out No. 2,494,256, and Lawson US. Patent No. 2,605,- 703, among others.

While the hollow or shaped explosive charge construction has many advantages, it also has substantial and serious limitations and disadvantages. In general, this type of charge construction is extremely sensitive to variations in the dimensions and configuration of its components. It is usually necessary to design a suitable apparatus by means of trial and error until particular dimensions and configuration of the components have been found to achieve satisfactory results. Even minor alterations in configuration and dimensions can cause a drastic reduction in the effectiveness of the device. The configuration and dimensions of the metal liner are of particularly great importance in apparatus employing the hollow explosive charge construction. Even where an optimum design has been developed, the reproducibility of apparatus employing this construction is somewhat unsatisfactory.

Also, explosive charges employing the hollow charge principle are highly sensitive to the stand-oft distance between the metal liner 0 fthe explosive charge and the ad jacent area to be penetrated or perforated. When an optimum stand-oft distance is not achieved or is substantially exceeds, satisfactory results are not obtained.

Another shortcoming of hollow charge explosive devices has been the difficulty in constructing a device whereby the metal liner will conform exactly to the shape of the hollowing of the explosive charge. This frequently requires delicate shaping operations.

In addition to overcoming the limitations of hollow charge explosive devices, an important feature and contribution of the present invention is to provide a means for introducing, in active form, a substance having a desired chemical, physical or physiological activity when propelled into the perforation made by the explosive charge assembly of the invention.

It is accordingly an object of the present invention to provide an improved explosive charge assembly which is free from the disadvantages of assemblies employing the hollow charge principle and which is not sensitive to variations in the dimensions and configuration of the components of the assembly.

It is another object of the invention to provide an explosive charge assembly suitable for military purposes which employs no hollowing of the explosive charge, but employs instead an explosive charge having a substantially planar or fiat face directed to the area to be penetrated or perforated and which employs in a lens element adjacent to the planar face of the explosive charge a chemical having desired chemical, physical or physiological action.

It is also an object of the present invention to provide an explosive charge assembly for perforating oil well casings and oil well boreholes employing a planar face of the explosive charge oriented toward the area to be perforated and which employs in a lens element adjacent to the planar face of the explosive charge a chemical having desired chemical or physical action when propelled into the adjacent earth formation.

It is a particularly important object of the invention to provide an explosive charge assembly which permits introduction, in active form, of a substance having a desired chemical, physical or physiological action when introduced into the penetration made by the explosive charge assembly of the invention.

The above-enumerated objects, as Well as other objects, together with the advantages of the invention, will be readily comprehended by persons skilled in the art upon reference to the present description, taken in conjunction with the accompanying drawing.

In the drawing:

FIGURE 1 is a longitudinal cross-section of a preferred construction of an apparatus of the invention, showing the parts, in the form of an explosive charge assembly suitable for perforating oil well casings and oil 3 well boreholes containing an active material in the lens element in accordance with the present invention.

FIGURE 2 is a longitudinal cross-section of another preferred form of the apparatus of the invention suitable for use in perforating oil well casings and oil well boreholes containing an active material in the lens element in accordance with the present invention; 7

FIGURE 3 is a longitudinal cross-section of a third form of the apparatus of the invention suitable for use in perforating oil well casings and oil well boreholes and especially adapted for use with active materials in the lens element which are liquids.

In the three figures of the accompanying drawing, the apparatus and its parts are shown in a scale one and onehalf times the actual size. It should be recognized that it is the practice in printing patents in the United States to reduce the size of the drawings by approximately 25%.

The objects of the present invention are accomplished by employing an explosive charge assembly in which the explosive material has a substantially planar face or surface oriented toward the opening of the assembly housing and facing toward the area which is to be perforated or penetrated. Adjacent to the substantially planar face of the explosive charge is the substantially planar face of a nonexplosive lens element with the lens having a concave hollowing facing away from the explosive charge, with the lens element comprising or containing a chemical substance having a desired chemical, physical or physiological action when propelled into the object to be penetrated by the explosive charge assembly. Superimposed over the concave hollowing of the lens element is a metallic liner. The features and construction of the apparatus of the invention will be characterized and explained in greater detail hereinbelow.

In order to describe the apparatus of the invention more clearly, reference will be made to FIGURES 1, 2, and 3 of the accompanying drawing wherein like parts will be similarly numbered. While the apparatus of the invention will be discussed primarily in connection with explosive charges as well. It is believed recognized by well casings and oil well boreholes, it is not intended that the invention shall be limited to such applications. It is intended that the apparatus of the invention shall be directed to and be applicable to military and industrial explosive charges as well. It is believed recognized by those skilled in the explosive art that the demands of military and industrial explosive charges are less acute and rigorous than those for perforating apparatus for use in oil well casings and boreholes. The major difference between military and industrial explosives on one hand and oil well explosives on the other is one of size, with oil Well explosives being, in general, substantially smaller than the others. Thus, the discussion of the apparatus of the invention in connection with the preferred embodiment illustrated in the drawing is done by way of illustration only and is not to be regarded in any way as a limitation in the scope of the invention.

The apparatus of the invention as illustrated by the three figures of drawing comprises an explosive charge gun 10, illustrated in the drawing in the form of a longitudinal cross-section thereof. The gun 10 comprises a housing 11 composed of any material capable of protecting the explosive charge from damage during handling. The housing material is preferably composed of a soft metal, such as lead or zinc, which gives increased confinement to the explosive detonation. Other materials have been employed as the housing material in devices of this kind and it is not contemplated that the nature of the housing material shall be limited. The housing 11 shown contains a centrally located fuse 12 in the opening 13. The fuse is desirably of a suitable material such as the well known Pn'macord fuse containing PETN (pentaerythrityl tetranitrate) or RDX (cyclotrimethylenetrinitramine) explosive. Packed adjacent to the fuse 12 in the opening 13 is the main mass of explosive charge substantial interference.

.and focused somewhat by the concave cavity of the lens 14 having a substantially planar face or surface 15. The nature of the explosive charge may vary, but a detonating explosive which is preferably of high density, such as a pressed or cast solid organic nitrate or nitro compound, is generally suitable. While any detonating explosive is generally satisfactory, high velocity or high order explosive charges are most suitable. Compressed PETN is one suitable material and compressed or cast blends of PETN with TNT, for example, in 50-50 mixtures, is also quite suitable. Similarl RDX is a suitable explosive as are its high density mixtures with TNT, one suitable blend consisting of parts of RDX in 20 parts of TNT. The foregoing explosive materials are particularly suitable since they possess high strength and upon detonation produce a high velocity detonation front, reaching maximum velocity very rapidly.

The construction shown by the three figures of the drawing differ only in the configuration and composition of the lens element and metal liner. In FIGURE 1 the lens element 16:: is made of compacted granular sulfamic acid with a planar face adjacent to the planar face 15 of the explosive charge 14. The lens element has a concave cavity 17a facing away from the explosive charge 14 and covering the cavity 17a is a metal liner 18a, of an alloy of lead and 10% antimony, being in the form of a truncated cone, with the cone walls meeting the Walls of the housing 11 at angles of 30 and having a curved apex of inch radius. This construction has been found to be particularly effective with the use of 20 grams of RDX as the explosive charge and 14 grams of sulfamic acid as the chemically active lens element.

FIGURE 2 illustrates another construction in which the lens element 16b is made of compacted sulfamic acid and the cavity 17b is covered by a parabolic liner 18b of copper 0.024 inch thick. Shown over the device is a protective cap 19 of suitable material such as aluminum.

The construction of FIGURE 3 shows the construction of a lens element of a type suitable with a compressed gaseous or liquid active agent. The lens element comprises a shell 16c containing a liquid Ztlc, such as hydrochloric acid and the metal liner 18c covering the concave cavity is made of lead antimony alloy. The shell 16c serves to protect the explosive 14 and the metal liner from the liquid contents.

While it is not intended to be bound by any theory or mechanism by which the apparatus of the present invention provides beneficial results, it is believed that upon the detonation of the explosive charge 14 by the fuse 12, a high velocity detonation wave is initiated flowing almost instantaneously from the fuse through the explosive charge and its substantially planar surface and the parallel facing planar surface of the lens elements 16a, 16b and 160 in the form of a shock wave. Where a high degree ofpenetration of the target is of paramount importance, it is desirable that the material of the active lens element be of a low density and particularly of a low ratio of specific gravity to average molecular weight. The'net effect here is that the shock wave is not reflected or diffused at the substantially planar or flat explosivelens element interface, i.e., no energy is lost since the shock wave has passed through the interface without The shock wave is transmitted element and upon the shock wave reaching the metallic body of the concave metal liners 18a, 18b and 180, the energy of the shock wave is accepted whereupon the liner becomes deformed and accelerated to form a hypervelocity stream of metal particles. -It is desirable that the metal liner have as poor an acoustical impedance, compressability and elasticity match with the material of the lens element so that maximum energy release will be obtained. The hypervelocity stream of metal which is produced from the metal liner provides the mass which is of importance in providing penetration of the target area. Following behind the hypervelocity stream of metal is a slower velocity stream of active lens element material surrounded by a high density gas cloud produced from the detonation of the explosive.

The hypervelocity stream of metallic particles can penetrate a considerable distance into a target material. For example, employing a construction as shown in FIG. 2, employing grams of RDX as explosive and 14 grams of crystahine su-lfamic acid as the lens material, and firing the charge assembly into three inches of No. 1020 mild steel target, with one-half inch stand-off provided by the protective cap 19 of aluminum, the perforation was found to have penetrated 2 /8 of the target steel.

It is particularly unique that when even a temperature-sensitive organic dye is mixed with the material of the lens element and the charge fired, tests have shown that the dye is found to penetrate predominately to the far end of the perforation. Tests indicate that the lens element material of the charge assembly of the invention is probably not subjected to temperatures of in excess of about 100 C. since, after firing, even temperaturesensitive lens materials are found to be undecomposed by the heat of detonation. This phenomenon makes a charge assembly of the present invention particularly useful for propelling chemically, physically or physiologically active substances effectively into a desired target area, without decomposition. These results contrast with those obtained using conventional shaped explosive charges. When a dye or other tracer material is mixed with the explosive in a conventional shaped or hollow explosive charge and the charge assembly detonated into a target, the dye or tracer material barely passes into the target area. Most of the dye material is scattered radially by the detonation with only a small fraction of the tracer material found at the immediate entrance of the perforation and none is found at the point of farthest penetration into the target.

A desirable lens element material, from the standpoint of maximum target penetration, may be characterized as one which has a low density and will transmit a shock wave while a desirable liner material may be characterized as one which has a high density and substantially accepts the shock wave energy.

The nature of the active or reactive lens material will depend upon the purpose for which the explosive charge assembly is to be employed and the nature of the target. The material may comprise liquids, solids, or liquefied gases and the material may provide chemical, physical or physiological action upon entering the perforation produced in the target. Preferably the lens material is solid, desirably finely-divided, and for the greatest penetration of the target area, the material shall have a ratio of specific gravity to average molecular weight of between about 0.0 and 0.5, with best results being obtained with a ratio of between about 0.0 and 0.05. Also, a material having a specific gravity of less than 2.5 is preferred, particularly when compressed.

For oil well borehole perforating the lens material desirably comprises an acid or a surface active agent. When employing an acid as the lens material, such as sulfamic acid, it has been found that even the small amount of acid which can be introduced into a miniaturized explosive charge assembly in accordance with the present invention for perforating oil well boreholes, such as 14 grams of sulfamic acid in each charge assembly, the breakdown pressures are less than when charges which do not employ the acid as lens material are used. Also, it has been found that the use of the sulfamic acid often eliminates the nee-d for separate and subsequent acid breakdown treatment. Among the acids which may be employed are: benzoic, bor-ic, citric, oxalic, picric, salicylic, sulfamic, acrylic, hydrochloric, nitric, sulfuric, nitrous, acetic, chloroacetic, hypochlorous, formic, phosphoric, oleic, linoleic acids, etc., with the solid acids being preferre The acids appear to assist in producing a larger perforation and they create a more porous perforaion, thereby improving the recovery of oil from the well.

Where desired, a base may be employed in the lens material such as hydroxides of alkali metals including sodium hydroxide and lithium hydroxide, higher molecular weight amines such as naphthylamine, dodecylamine, LZ-benZenediamine, etc. and ammonia and low molecular weight amines such as ethylamine, dibutylamine, trimethylamine, diethylenetriarnine, aniline, pyridine, etc.

Also, for oil well applications it is frequenty desirable to introduce a surface active agent in solid, solution or suspension form into an oil well and this can be done in accordance with the present invention. The surface active agents assist in the removal of crushed earth material from the pores of the perforated body and subsequently the recovery of oil from the formation is enhanced. Among the surfactants which may be employed are: sodium dodecylbenzene sulfate, ethylene oxide adducts of oleyl alcohol, dodecyl ammonium chloride carried in water or water-alcohol mixtures, etc. and oil solutions or suspensions of fatty acid amine salts such as dodecylamine oleate, mahogany sulfonates, sorbitan monooleate, etc.

it is frequently desirable to trace the position of the perforation and for this purpose it is desirable to employ'as the lens material a tracer material such as a radioactive material or a fluorescent dye. Radioactive materials may include radioactive iodine dissolved in oil or a uranium salt such as uranium hexafiuoride. Among the fluorescent dyes are fluorescein dissolved in an alkali aqueous solution.

Oxidizing agents or chemical salts may be suitably employed as the lens material and material such as potassium permanganate, sodium perchlorate, sodium carbonate, potassium nitrate, calcium chloride, etc. may be employed for this purpose.

For military purposes the desirable reactive lens material may take several forms such as incendiary materials, chemical warfare materials, such as lachrymators, physiological agents such as nerve gases, biological warfare agents such as viruses, disease producing bacteria, or smoke generating substances. Among the incendiary materials which may be employed are thermit, yellow phosphorus, iodine pentobromide, bromine tetrafluoride, chr0- mic acid, sodium peroxide, etc. Among the lachrymators are benzyl bromide, bromo acetone etc. The physiological agents may include the nerve gas Tabun (cyanodimethylaminoethoxy phosphine oxide). The biological agents may include virulent viruses and bacteria known to be useful in biological warfare. Suitable smoke generating substances include such materials as phosphorus, titanium tetrachloride, etc.

in the military explosive charge assemblies of the invention, the reactive lens material is injected into the target after the hypervelocity stream of metal and thereupon performs its intended role. Thus if the reactive lens material is an incendiary material, it will follow the stream of metallic particles from the disintegrated metal liner into the target and induce combustion internally in the military tank, fuel dump, ship, or the like. If the reactive lens material is a chemical or biological warfare material it is injected into the steel walls of the target building, vehicle or vessel and renders the crew helpless and permits their capture intact with equipment, documents and maps. Or, in the case of buildings storing foods and supplies, renders the contents useless to the enemy. Weapons capable of accomplishing such results have long been sought by the military.

When desirable other chemical materials of various classes, including alcohols, esters, ketones, hydrocarbons, both aliphatic and aromatic, chlorinated hydrocarbons and compressed or liquefied gases may be employed as the lens material.

When employing strongly oxidizing substances or incendiary substances it is desirable to encase the substance in a shell of lead or some other unreactive material and employ assembly construction of the type iilustrated by FIG. 3.

Among the most preferred reactive lens materials from the standpoint of providing maximum penetration are the following lens materials and their ratio of specific gravity to average molecular weight.

Ratio of specific gravity to average Lens material: molecular Weight The concave metal liner is desirably of a substance which is a poor conductor or transfer agent of the shock wave. It desirably has a high mass or specific gravity and is desirably of a metal melting below about 500 C. Among the suitable materials for the concave metallic liner are copper, aluminum, steel or brass. Desirably a low-melting metal having a melting point of 500 C., such as zinc, Babbit metal, lead, cadmium, zinc, solder, and alloys of these materials. The low melting metals are preferred because they have less tendency to produce a carrot or slug of metal in the area penetrated or perforated. However, when employing a chemically reactive lens element material, such as an acid, even the higher melting lens materials show less of a tendency to form a carrot or slug.

The essential configuration of the reactive lens element is that it have a substantially planar or fiat surface adjacent to the substantial planar surface of the explosive charge and at its opposite end a hollowing or concave cavity. The essential configuration of the metal liner is that it have a concave cavity and be contiguous with the concave cavity of the lens element. The cavities of the lens element and the metallic liner may take any form including conical, hyperbolic, parabolic, ellipsoidal, hemispherical, pyramidal, and variations of these. The metal liner is desirably placed contiguous with the concave cavity of the lens element with the apex of the metal liner in close proximity or adjacent to the planar surface of the explosive charge. It is not necessary, and not desirable, that the liner be in contact with the explosive charge, as in the case of the hollow charge devices of the prior art.

The metal liner may vary in thickness. Desirably the liner is thick enough to absorb sufiicient shock wave energy so that it provides a hypervelocity stream of metal. It should not be so thick that its large inertia prevents formation of a hypervelocity stream of metal.

One of the important advantages of the apparatus of the present invention is that it is substantially free from sensitivity to variations in the dimensions and configuration of its components. Excellent results can be obtained regardless of variations in the dimensions and configuration of the components, so long as the essential planar interface exists between the explosive charge and the lens element and so long as the lens element and the concave metal liner are adjacent to each other and of the same relative configuration. Thus, the apparatus of the invention will provide reproducible results over a wide range of dimensions and configurations. Also, explosive charge assemblies in accordance with the present invention are not sensitive to variations in stand-off distance between the metal liner and the adjacent area to be penetrated.

Since the apparatus of the present invention is not sensitive to variations in dimensions and configuration of its components, the maximum energy of the explosive shock wave can readily be transmitted to provide maximum penetration. The limiting factor is the supply of shock wave energy which the explosive charge will provide and not the particular efficiency or configuration of the lens element-liner combination. This is a p int of major difference between the explosive charge assembly 'of the present invention and devices based on the hollow charge principle. Simply by enlarging the area of the contact between the'explosive charge and the reactive lens element at the adjacent substantially planar interface, the energy supply can be materially increased. Since the area of a circle increases as the square of its radius, by multiplyin g the radius of the substantially planar interface between the explosive charge and the lens element by two, it is possible to increase the available energy by four times. The lens element and particularly the metallic liner serve to focus this energy and produce a highly effective hypervelocity force.

Military explosive charge assemblies in accordance with the present invention may be utilized in a way with which those skilled in the art are familiar and by incorporating the explosive charge assembly, with its reactive lens material, in suitable projectiles, shells and the like, such as the Bazooka. For oil well casing perforating, the explosive charge assemblies of the invention may be employed in accordance with techniques well known to those skilled in the art. The apparatus of the invention may be employed merely to perforate oil well casings or boreholes or they may be employed to perforate casings or boreholes as part of a process of fracturing the earth formation. Desirably, by employing the explosive charge assemblies of the present invention in the fracture initiating apparatus disclosed in the pending U.S. application of Bruce Gilbert, Ser. No. 675,424, filed July 31, 1957 to replace the corresponding hollow charge assemblies disclosed therein, excellent results may be obtained upon subsequent treatment of the oil well with a fracturing fluid in accordance with the process as that disclosed in US. patent application of Bruce Gilbert, Ser. No. 700,144, filed December 2, 1957. It is intended to incorporate the disclosures of these two copending applications in their entireties.

Illustrative of the results which may be obtained employing the explosive charge assemblies of the present invention is an oil well field test which will be described hereinbelow. It should be understood, however, that this is done solely by way of example and is intended neither to delineate the scope of the invention nor limit the ambit of the appended claims.

Field test Employing explosive charge assemblies in accordance with the construction illustrated by FIGURE 2 of the drawing, having a housing 11 with a Primacord fuse 12 and an explosive charge 14 of 20 grams of RDX having a planar interface 15 between the explosive charge 14 and the lens element 16b, comprising 14 grams of compacted granular sulfamic acid, and a parabolic metal liner of copper 0.024 inch thick, an oil well, having a casing of 4 /2 inches diameter, was subjected to the firing of 24 of said explosive charges spaced two per foot. The firing took place at a depth of 2753 to 2757 feet and 2760 to 2768 feet. After firing the explosivecharge assemblies, the firing mechanism was removed from the well. The 'well gave up free oil after this perforating treatment without any stimulating or fracturing. None of the other wells in this area had given up oil when perforated by other types of explosive charge assemblies, unless stimulated or fractured. To increase the output of the well to commercial quantities, the oil Well was acidized With 250 gallons of muriatic acid and then subjected to a fracturing treatment with 10,000 gallons of lease crude containing 20 gallons of non-ionic Wetting agent and one-twentieth of a pound per gallon of sodium dodecylbenzene sulphonate containing sodium sulfate as an inert filler. The residual crude oil contained 22,000 pounds of sand to function as a propping agent. The fracturing fluid accomplished a breakdown at 1700-1950 pounds per square inch pressure which was good for oil wells in this area.

The terms and expressions employed are used as terms of description and not of limitation, and it is not intended, in the use of such terms and expressions, to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. An explosive charge assembly comprising a container housing having an open end and containing a detonatable explosive charge having a substantially planar surface oriented toward the open end of said container housing, a lens member of a non-explosive substance having a substantially planar surface adjacent to and in contact with said substantially planar surface of said explosive charge and having a concave cavity oriented toward the open end of said container housing, said nonexplosive substance being undecomposed by the heat of detonation of the explosion and being reactive when propelled into the object to be penetrated by the explosive charge assembly, and a metallic liner superimposed over the concave cavity of the lens element.

2. An explosive charge assembly as defined by claim 1, wherein the explosive charge is a high velocity explosive.

3. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises a non-metallic solid having a specific gravity of not more than about 2.5.

4. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises a substance having a ratio of specific gravity to average molecular weight or" between about 0.0 and 0.5.

5. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises a substance having a ratio of specific gravity to average molecular weight of between about 0.0 to 0.05.

6. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises a lachrymator.

7. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises an incendiary substance.

8. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises a chemical warfare agent.

9. An explosive charge assembly as defined by claim 1, wherein the reactive lens member comprises a biological warfare agent.

10. A well borehole casing perforating apparatus comprising a container housing having an open end and containing a detonatable explosive charge having a substantially planar surface oriented toward the open end of said container housing, a lens member of a non-explosive substance having a substantially planar surface adjacent to and in contact with said substantially planar surface of said explosive charge and having a concave cavity oriented toward the open end of said container housing, said nonexplosive substance being undecomposed by the heat of detonation of the explosion and being reactive when propelled into the object to be penetrated by the explosive charge assembly, and a metallic liner superimposed over the concave cavity of the lens element.

11. A well borehole casing perforating apparatus as defined by claim 10, wherein the explosive charge is a high velocity explosive.

12. A well borehole casing perforating apparatus as defined by claim 10, wherein the lens member comprises a non-metallic solid having a specific gravity of not more than about 2.5.

13. A well borehole casing perforating apparatus as defined by claim 10, wherein the reactive lens member comprises a substance having a ratio of specific gravity to average molecular weight of between about 0.0 and 0.5.

14. A well borehole casing perforating apparatus as defined by claim 10, wherein the reactive lens member comprises a substance having a ratio of specific gravity to average molecular weight of between about 0.0 to 0.05.

15. A well borehole perforating apparatus as defined by claim 10, wherein the reactive lens member comprises sulfamic acid.

16. A well borehole perforating apparatus as defined by claim 10, wherein the reactive lens member comprises an acid.

17. A well borehole perforating apparatus as defined by claim 10, wherein the reactive lens member comprises abase.

18. A well borehole perforating apparatus as defined by claim 10, wherein the reactive lens member comprises a surface active agent.

19. A device for producing a directed pressure-wave comprising; a cone having an apex and a forwardly opening concave surface and a rearwardly facing convex surface; a body of explosive located opposite said rearwardly facing surface and adjacent said apex, said convex surface and said body of explosive defining a space therebetween with said apex being closer to said body of explosive than any other part of said convex surface; a body of non-explosive liquid pressure-wave transmission medium substantially filling said space defined by the said rearwardly facing surface of said cone and said explosive body; and means for detonating said explosive body.

20. A device for producing a directed pressure-wave comprising: a cone having an apex and a forwardly opening concave surface; a body of explosive having a substantialy flat forward surface adjacent said apex, said cone and said forward surface of said body of explosive defining a space therebetween; a body of nonexplosive liquid pressure-wave transmission medium substantially filling said space defined by said cone and said surface; and means for detonating said explosive body.

21. A device according to claim 19 wherein said pressure-wave transmission medium is an acid.

22. A device according to claim 19 wherein said pressure-wave transmission medium is hydrochloric acid.

References Cited by the Examiner UNITED STATES PATENTS R6. 21,356 2/40 Pitzer 102-21 2,605,703 8/52 Lawson 102-2O 2,628,559 2/53 Iasse 102--24 3,054,938 9/62 Meddick 102-20 FOREIGN PATENTS 693,164 6/53 Great Britain.

SAMUEL FEINBERG, Primary Examiner. SAMUEL BOYD, ARTHUR M. HORTON, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 5 ,188 955 June 15, 196

William E. Brown It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 13, for "exceeds" read exceeded column 3, line 40, strike out "charges as well. It is believe recognized by" and insert instead charge assemblies suitabl for perforating oil column 10, lines 43 and 44, for "substantialy" read substantially Signed and sealed this 23rd day of November 1965.

SEAL) \llest:

ERNEST W. SWIDER EDWARD J. BRENNER meeting Officer Commissioner of Patents 

1. AN EXPLOSIVE CHARGE ASSEMBLY COMPRISING A CONTAINER HOUSING HAVING ANOPEN END AND CONTAINING A DETONATABLE EXPLOSIVE CHARGE HAVING A SUBSTANTIALLY PLANAR SURFACE ORIENTED TOWARD THE OPEN END OF SAID CONTAINER HOUSING, A LENS MEMBER OF A NON-EXPLOSIVE SUBSTANCE HAVING A SUBSTANTIALLY PLANAR SURFACE ADJACENT TO AND IN CONTACT WITH SAID SUBSTANTIALLY PLANAR SURFACE OF SAID EXPLOSIVE CHARGE AND HAVING A CONCAVE CAVITYH ORIENTED TOWARD THE OPEN END OF SAID CONTAINER HOUSING, SAID NONEXPOLOSIVE SUBSTANCE BEING UNDECOMPOSED BY THE HEAT OF DETONATION OF THE EXPLOSION AND BEING REACTIVE WHEN PROPELLED INTO THE OBJECT TO BE PENETRATED BY THE EXPLOSIVE CHARGE ASSEMBLY, AND A METALLIC LINER SUPERIMPOSED OVER THE CONCAVE CAVITY OF THE LENS ELEMENT. 